1. Field of the Invention
This invention relates to a composition useful as a coating and lubricating finish for surgical sutures. More particularly, this invention relates to a means for improving the tie-down properties of multifilament, absorbable sutures by coating the sutures with a single-component, absorbable composition comprising a fatty acid salt applied to the suture from a gel of the salt in a volatile organic solvent.
2. Description of Prior Art
Suture materials are generally classified as either absorbable or nonabsorbable, with each type of suture material being preferred for certain applications. Absorbable suture materials are preferred for internal wound repair in which the sewn tissues will hold together after healing without suture reinforcement and in which a nonabsorbed suture may promote tissue irritation or other adverse bodily reaction over an extended period of time. Suture materials are considered to be absorbable if they disappear from the sewn tissue within about a year after surgery, but many absorbable suture materials disappear within shorter periods.
The earliest available absorbable suture materials were catgut and extruded collagenous materials. More recently, absorbable sutures derived from synthetic polymers have been developed which are strong, dimensionally uniform, and storage-stable in the dry state. Typical of such polymers are lactide homopolymers, and copolymers of lactide and glycolide such as those disclosed in U.S. Pat. No. 3,636,956, and glycolide homopolymers such as those disclosed in U.S. Pat. No. 3,565,869, both patents being incorporated herein by reference.
Monofilament synthetic absorbable suture materials are generally stiffer than their catgut or collagen counterparts, and synthetic absorbable sutures are therefore usually employed in a multifilament, braided construction in order to provide the suture with the desired degree of softness and flexibility. Such multifilament sutures often exhibit a certain degree of undesirable roughness or "grabbiness" in what has been termed their "tie-down" performance, i.e., the ease or difficulty of sliding a knot down the suture into place.
Multifilament nonabsorbable sutures such as braided sutures of polyethylene terephthalate, for example, can be improved with respect to tie-down performance by coating the external surface of the suture with solid particles of polytetrafluoroethylene and a binder resin as disclosed in U.S. Pat. No. 3,527,650. This procedure, however, is undesirable as applied to absorbable sutures because polytetrafluoroethylene is nonabsorbable and sutures coated therewith would leave a particulate residue in the sewn tissue after the suture had absorbed.
Multifilament, nonabsorbable sutures can also be improved with respect to tie-down performance by coating them with a linear polyester having a molecular weight between about 1,000 and about 15,000 and at least two carbon atoms between the ester linkages in the polymer chain as disclosed in U.S. Pat. No. 3,942,532. This patent discloses that the aforementioned polyesters may also be used to coat absorbable synthetic sutures, but does not consider that such coated sutures would not be totally absorbable.
U.S. Pat. No. 3,297,033 discloses that absorbable polyglycolic acid sutures may be coated with conventional suture coating materials such as a silicone or beeswax in order to modify the handling or absorption rate of the sutures. These coating materials are not readily absorbable, however, and will accordingly leave an undesirable residue in the tissue after the suture itself is absorbed.
An absorbable, three-component composition for coating absorbable sutures is described in my earlier patent, U.S. Pat. No. 4,027,676. This coating comprises a combination of a film-forming polymer such as a lactide or glycolide homopolymer or copolymer, a lubricant which is preferably a polyalkylene glycol, and a hydrophobic component which is preferably a higher fatty acid or ester. While this composition gives good results, it requires the formulation of a multicomponent system, and is accordingly less convenient to use than the single-component coating composition of the present invention.
It is accordingly an object of the present invention to provide an absorbable, lubricating coating for multifilament sutures of braided, twisted or covered construction. It is a further object of this invention to provide an absorbable coating to improve the tie-down properties of such multifilament sutures. It is a yet further object of this invention to provide a single-component composition useful as a coating to improve the tie-down properties of absorbable, multifilament sutures.